Gear pump or motor



Dec. 4, 1956 Filed Sept. 13, 1950 J. NAGELY 2,772,638

GEAR PUMP 0R MOTOR 5" Sheets-Sheen 1 IN VEN TOR.

Johnllfyc gez pw muk m Dec. 4, 1956 J. LINAGELY GEAR PUMP OR MOTOR 3 Sheets-Sheen 2 Filed Sept. 13, 1950 73 55 mmvron ggohnl 11/6 85 Dec. 4, 1956 L. NAGELY 2,772,638

GEAR PUMP 0R MOTOR Filed Sept. 13-, 1950 s Sheets-Sheep 3 INVENTOR. 76 finLAiji/y United States Patent GEAR PUMP on MOTOR John L. Nagely, Lagrange, Ohio Application September 13, 1950, Serial No. 184,612

22 Claims. (Cl. 103-126) This invention relates to high pressure gear-type liquid displacement devices such as hydraulic pumps or motors.

In the high pressure gear pump art, arrangements have heretofore been proposed whereby the discharge pressure of the pump is utilized to maintain a pumping seal between axially adjustable end plates or bushings and the associated gears. In such prior art arrangements, counterbalancing pressure chambers are provided between the outer faces of the end plates or bushings and the adjacent portions of the pump casing or housing, and high pressure discharge fluid is supplied to these pressure chambers whereby to effect the desired pressure loading of the end plates. As a result, the pump casing in the areas adjacent the end plates or bushings is subjected to extremely high pressures and must, therefore, possess a high degree of structural strength.

I have found that by providing counterbalancing pressure chambers or zones which are separate from and substantially independent of the pump casing I am able to obtain the desired pressure loading of the end plates or bushings while at the same time permitting the reaction within such chambers to be taken up by the internal pump assembly without imposing pressures of high mag nitude against the adjacent portions of the pump casing.

Although for the sake of simplicity the invention is described hereinafter in the specification and claims primarily with reference to a gear pump, it will be understood that the principles here involved are applicable to gear-type liquid displacement devices generally, including both hydraulic gear pumps and motors.

Accordingly, a primary object of my invention is to provide a novel and improved pressure loading arrangement for a gear-type liquid displacement device wherein movable end plates or bushings are effectively maintained in desired sealed relation with the adjacent gears by means of high pressure working fluid.

Another object of the invention is to provide a novel pressure loading arrangement as described above wherein the casing of the device in the areas adjacent the end plates or bushings is not subjected to the high counterbalancing pressure.

A further object of the invention is to provide a novel pressure loading arrangement as described above wherein the reaction is taken up within the internal gear assembly of the device rather than by the casing or cover portions of the device.

Still another object of the invention is to provide a gear-type liquid displacement device having a novel pressure loading arrangement as described above wherein the entire internal operating structure of the device is constructed as a unit assembly which is readily removable from an external housing or casing.

Other objects and advantages of the invention will become evident from the subsequent detailed description taken in connection with the accompanying drawings,

wherein I Fig. 1 is an end view of a gear pump comprising one specific embodiment of my invention;

Fig. 2 is an enlarged longitudinal sectional view taken along the line 2-2 of Fig. 1;

Fig. 3 is a transverse sectional view taken along the line 3-3 of Fig. 2;

Fig. 4 is a perspective view of an internal unit assembly of the device as removed from its casing or housing;

Fig. 5 is an elevational view of the inside face of one element of the device shown in Figs. 1 to 4;

Fig. 6 is a sectional view taken along the line 66 of Fig. 5;

Fig. 7 is a sectional view taken along the line 77 of Fig. 5;

S is a sectional view taken along the line 8-8 of Fig. 5;

Fig. 9 is a sectional view similar to Fig. 2 but showing a modified form of the device;

Fig. 10 is a fragmentary sectional view taken along the line lt?--1t) of Fig. 9;

Fig. 11 is an elevational view of the outside face of one element of the device shown in Fig. 9;

Pg. 12 is an elevational view of the opposite face of the element shown in Fig. 11;

Fig. 13 is a sectional view taken along the line 13--13 of Fig. 12; and

Fig. 14 is a sectional view taken along the line 14-14 of Fig. 12.

Briefly, my invention involves a gear-type liquid displacement device, specifically a gear pump, in which a pair of axially adjustable end plates are disposed at the opposite faces of the gears with the gear shafts extending through the end plates and journaled therein. For urging the end plates inwardly against the gears in operative sealed relation therewith, pressure chambers are provided adjacent the outer faces of the end plates which chambers are in fluid communication with the discharge outlet of the pump and are effectively sealed oif from the adjacent portions of the pump cover or casing so that the reaction from the pressure chambers is not transmitted to the pump casing. As will hereinafter appear, in the preferred embodiments of my invention, annular thrust bearings are disposed around the gear shafts and are held in place by means of retainer nuts threaded to the opposite ends of the shafts. The thrust bearings are formed with portions spaced outwardly from the end plate structures to provide a plurality of annular zones adapted to receive high pressure discharge fluid for effecting the desired pressure loading of the end plates. As a result of this construction, the reaction against the thrust bearings is resisted by the gear shafts and consequently the high pressures inherent in a pressure loading arrangement are prevented from being exerted against the adjacent ends of the pump casing. In addition, the entire inner working portions of the device, including the gears, end plates, and pressure loading fluid supply means, are constructed as a unit assembly which is readily removabie from the casing.

Referring now to Figs. 1 to 8 of the drawings, one embodiment of my invention shown merely by way of illustration comprises a gear pump having an external casing or housing, indicated generally at 20, and an internal unit assembly, indicated generally at 21, the latter constituting the operating mechanism of the pump and being readily removable as a unit from the housing 20. The external casing 20 consists of a high strength central body portion 22.having a fluid inlet port 23 and an outlet port 24 (Fig. 3), a cover portion 25 at one end of the body portion 22, and a cover portion 26 at the opposite end of the device including a driving means and seal means, indicated generally at 27. The cover portions 25 and 26 are removably secured to the body portion 22 by means of a pair of screws 28 extending through the cover por- 3? tions and threaded into the body portion and also by means of a plurality of elongated screws 29 extending through suitable bores in the cover portion 25 and the body portion 22 and threaded into the opposite cover portion 26. Inasmuch. as the details of the driving and sealing means 27 do not constitute any part of the present invention, further description of this portion of the device is unnecessary.

The internal unit assembly 21 comprises a drive gear 31 carried integrally on a gear shaft 32 having an axial bore 33, and a driven gear 34 meshed with the gear 31 and carried integrally on a gear shaft 36 having an axial bore 37. The gears 31 and 34 are surrounded by the body portion 22 of the pump casing to provide an inlet or low pressure pump chamber 38 (Fig. 3) adjacent the port 23 and an outlet or high pressure pump chamber 39 adjacent the port 24. The end of the drive gear shaft 32 adjacent the cover 26 carries an extension formed with a male drive spline 41 which is detachably fitted into a complementary female spline connection in the drive means 27.

In order to provide a pumping seal with the gears 31 and 34, a pair of end plates 42 are disposed at the opposite side faces of the meshed gears, each end plate having a lower bore 43 and an upper bore 44 constituting bearing journals through which the gear shafts 32 and 36 extend at their opposite ends. The external contour of the end plates 42 is formed to permit a close clearance sliding fit in the body portion 22 of the housing. Encircling the outer end portions of the gear shafts 32 and 36 are annular thrust bearings, indicated at 46, each having an inwardly extending rim or lip portion 47 in operative engagement with the outer face of the adjacent end plate 42 whereby to provide a plurality of annular pockets or pressure chambers 48 adapted to receive high pressureworking fluid for urging the end plates 42 inwardly toward the gears 31 and 34. A retainer nut 49 is threaded to each end portion of the gear shafts 32 and 36 for adjusting the clearance between the thrust bearings 46 and the end plates 42 and for establishing a maximum clearance between the end plates 42 and the gears 31 and 34. The nuts 49 at the ends of the internal unit assembly 21 are spaced inwardly from the adjacent covers and 26 to provide a pair of cover chambers 50 and 51 which are in fluid communication through the gear shaft bores 33 and 37 for receiving working fluid under relatively low pressures, as hereinafter described in detail.

In order to provide integral bearing surfaces for the moving parts of the device, the inner circumferences of the bores 43 and 44 in the end plates 42 and also the inner and outer flat faces of the end plates 42 may be surfaced with a suitable bearing material as indicated at 52 (Fig. 2). For example, the end plates 42 may conveniently be formed from a high strength alloy steel in order to resist deflection of the end plates under high pressure loads, and the bearing surfaces may comprise a lead bronze bearing material which may be applied in any suitable manner such as by spraying or plating. Under other conditions where high structural strength is not required, the entire end plates 42 may be formed from lead bronze or other bearing material in which case the gear shafts 32 and 36 may be journaled directly in the bores 43 and 44 of the end plates.

Annular seals, indicated at 53, are disposed between the thrust bearings 46 and the gear shafts. In addition, a pair of ring seals 54 are provided at the juncture of the end plates 42, the body portion 22 of the casing, and the casing covers 25 and 26 in order to insure a satisfactory seal between the discharge chamber 39 and the cover chambers 50 and 51 and also between the cover chambers and the exterior of the pump. Other suitable sealmg means may also be employed. For example, the outer contours of the end plates 42 may be surfaced with a layer of resilient sealing material such as synthetic rubber which is compressed to provide a tight seal when the end plates are in assembled position in the casing.

By means hereinafter described, working fluid under discharge pressure is supplied from the high pressure or discharge chamber 39 of the pump through suitable valved passageways in the end plates 42 to the annular pressure chambers 48. Thus, a force is provided tending to urge each of the end plates 42 inwardly against the side faces of the gears 31 and 34 to provide a pumping seal therewith and the reaction from this force against the end plates is transmitted through the thrust bearings 46 and the nuts 49 to the opposite ends of the gear shafts 32 and 36 thereby placing the latter under tension. Consequently, it will be seen that the shafts 32 and 36 function as tension members for taking up the entire reaction forces from the pressure loading with the result that the covers 25 and 26 of the pump casing are not subjected to the high dis charge pressure of the pump and therefore do not require the high structural strength material employed in the body portion 22 of the pump casing.

By proper correlation of the effective exposed areas of the end plates 42 both in the discharge chamber 39 of the pump and in the annular pressure chambers 48, the pressure within the chambers 48 results in a total unbalanced force exerted inwardly on the end plates which is always greater than the total force exerted outwardly against the end plates by the high pressure discharge fluid in the discharge chamber of the pump. This area relationship may be selected to provide any desired predetermined unit pressure loading between the inner faces of the end plates and the rotating side faces of the gear. As a result of the unbalanced forces exerted on the end plates by high pressure discharge fluid in the annular pressure chambers 48 and in the discharge chamber 39 of the pump, it will be seen that a small but finite clearance exists between the coacting surfaces of the gears and the end plates and the latter in effect float between the side faces of the gears and the thrust bearing surfaces with a predetermined minimum clearance.

During operation of the pump, the nuts 49 and the thrust bearings 46 rotate with the gear shafts 32 and 36, and the thrust bearings 46 are lubricated by leakage of high pressure fluid radially from the chambers 48 between the end plates 42 and the rotating thrust bearing lip portions 47 into the cover chambers 50 and 51. As will hereinafter appear, the cover chambers 50 and 51 are vented through suitable valved passageways in the end plates 42 to the low pressure or inlet chamber 38 of the pump so that the cover chambers are subjected only to relatively low fluid pressures and the rotating thrust bearings 46 and retainer nuts operate while surrounded by low pressure working fluid. By adjustment of the thrust bearings 46 by means of the nuts 49, the maximum clearance between the end plates and the gears is determined, and in addition the clearance between the outer faces of the end plates 42 and the thrust bearing lip portions 47 is controlled in order to minimize leakage of high pressure fluid at this point. By restricting the extent of leakage of high pressure fluid from the annular chambers 48 to the cover chambers 50 and 51 to a relatively small amount, adequate lubrication of the thrust bearings is maintained without materially affecting the volumetric efficiency of the pump.

Lubrication of the radial bearing surfaces or journals of the gear shafts 32 and 36 is accomplished by leakage of high pressure working fluid from the annular pressure chambers 48 axially along the bearing journals 43 and 44 toward the end plate-gear face bearing surfaces and thence into the low pressure chamber 38 at the inlet of the pump. In order to insure that the leakage of high pressure fluid along the bearing journals is suflicient for lubricating purposes, I preferably provide the inside faces of the end plates 42 with a pair of semi-annular grooves 57 (Pig. 5) which extend concentrically around a substantial portion of the bores 43 and 44. Fluid communication between the bearing journals and the grooves 57 is established by means of a minute radial metering groove or scratch 58 mace of predetermined sizev which extends. from each off thebearing journals 43 and 44 to. an' intermediate: P0111011 of the corresponding semi-annular groove: 57 whereby fluid.

flows from the. bearing journals through the grooves'58 and 57 and the adjacent end plate-gear face interfaces into the low pressure inlet chamber38of the .pump.. Thus, a controlled flow of high pressure fluid is permittedralong. the bearing journals 43 and 44 which is in excess; of the normal leakage through the pumping seal at the end plate gear face surfaces.

For augmenting the normal lubrication of the end plate-gear face surfaces by the working fluid in the. inlet and outlet chambers of, the pump, the ends of the 361111: annular grooves 57 terminate. in transversely extending bores, indicated at 59 (Fig. 7), which. extend from spaced points at. the inside faces. of the end plates 42 within the root circles of the gears 31 and 34 to the annular pressure chambers 48 at the outside faces of the end plates. Lubricating fluid thereby is permittedto fi'ow fromthe annular chambers 48 inwardly through the bores 59 to the opposite ends of the semi-annular grooves-57 whereby to insure that the grooves 57 are filled at all times with working fluid. Consequently, adequate lubrication of the end plate-gear face surfaces is realized under all conditlons and such fluid is vented from'the grooves 57 at the low pressure or inlet side of pump.

In order to supply high pressure working fluid from the discharge chamber 39 of the pumpto the annular pressure chambers 48, each of the end plates 42' ispro vided with a double set of internal unidirectional check valves and communicating fluid passageways which'permit' reversible operation of the device merely by changing the direction of rotation of the gears 31 and 34. Referring particularly to Figs. to 8, the inside face of each end plate 42 is Provided with a pair of oppositely disposed shallow recesses or cavities 61 and 62' located. at the central portion of the end plate intermediate the upper and lower bores 44 and 43. For purposes of explanation, in Figs. 5 to 8 the recesses 61' and 62 will be considered as being disposed within the high pressure or discharge chamber 39 and the low pressure or inlet chamber 38 of the pump, respectively.

The recesses 61 and 62 communicate with a pairv of outermost valve chambers or bores, indicated at 63 and 64, respectively (Fig. 8), which contain spring-pressed ball check valves as at 66 and 67, respectively The valve chambers 63 and 64 have their outermost ends sealed by means of a pair of plugs 68 and are,. therefore, in fluid communication with only the inner. chambersv of the pump. A pair of innermost valve chambers or bores, in.- dicated at 69 and 71, are also provided in eachof the end plates 42 intermediate the bores 63 and 64 and are in fluid communication with the recesses61. and 62, respectively. The valve chambers 69 and 71 contain a pair of spring-pressed ball. check valves. 72 and 73,. respectively, which are in oppositely disposed relation with respect to the valves 66 and 67. The valve chambers or bores 69 and 71 have ports at their opposite ends toprovide fluid communication completely through the end plates 42 in order to permit controlled fluid flow from the cover chambers 50 and51 throughthe end plates. to the inlet chamber of the pump, as hereinafter described in detail. Fluid communication between the valvechamber 63 and the annular pressure chamber 48 in each end plate is established by means of an angularly disposed bore 74 (Fig. 6), extending upwardly from the valve chamber 63 to the annular pressure chamber- 48 around the gear shaft 36 and by a similar internal bore (not shovm) extending downwardly. to the annular chamber 48 around the gear shaft 32. A corresponding pair of angularly extending bores (not shown) are also provided between the valve chamber 64 and the. upper and lower annular chambers 48.

The flow of high pressure working fluid to the annular the gear shafts, indicated at 79 and 81.

the pump and presses the ball check valve 66 inwardly to open position with the oppositely disposed ball check valve 72remaining closed. High pressure fluid flows from the valve chamber 63 through the angular bores 74 to'the' annular pressure chambers 48. As the cover chambers and 51 at the opposite endsofthepump fill with working fluid at reduced pressure, in. the. manner hereinbefore described, the. pressure within the cover chambers 50 and 51 increases. When this pressure reaches a value in excess of the pressure at the inlet side of the pump, the ball check valve 73 is urged inwardly in the valve chamber 71. and the working fluid is thereby vented from the cover chambers through the valve chamber 71 and the recess 62. to'the inlet or low pressure chamber 38 of the pump. During; this venting action, the ball check valve 72 remains closed because the pressure of the discharge fluid from the. recess 61 urging the valve 72 closed is greater than the pressure within the cover chamber acting on the other side of the valve 72. In addition, the ball check valve 67 remains closed because the pressure of its spring is? greater than the inlet pressure the chamher-38..

Because of the double arrangement. of unidirectional check valves, it will be seen that my device is readily reversible merely by reversing the direction of rotation of the drive gear 31 and thereby reversing the direction of fluid flow through the pump. Thus, in the above description the recess 61 of each end plate 42 is disposed at the high'pressurc or discharge side of the pump, the recess. 62.0perates in the low pressureor inlet chamber of thepump, and the valves66 and 73 are the only valves in operation, the valves 67 and 72' remaining closed. However, upon reversal of the driving mechanism of the pump, the recess 62 is now disclosed at the discharge or high pressure side of, the pump and the recess 61 is at the low pressure or inlet side of the pump. It will be apparent that under such conditions the valves 67 and 72 will thenoperate to supply high pressure fluid to the pressure. chambers 43 and to vent the working fluid from the cover chambers. to the inlet side of the pump with the valves 66 and' 73 remaining closed.

Reference now is made to Figs. 9 to 14 of the drawings Whereinamodified form of gear pump is illustrated having separate bearing bushings in the end plates for journalingthe. opposite ends of: the gear shafts. For certain uses: of mygear pump, for example at relatively high operating temperatures, it'may be found necessary to construct the. end plates from a different material than the gear shafts. As a result of the different structurai materials of the end. plates and gear shafts, differential expansion can occur. which makes it impractical to empioy the integral radial bearing construction illustrated in Figs. 1 to 8. Also, in. certain cases where foreign material may occur in the working fluid it may be preferable to employ a different bearing arrangement from that shown in Figs. 1 to 8.

In the'embodiment shownin Figs. 9 to 14, the general arrangement of the. pump casing having the working parts of thepump removabl'y disposed therein as a unit assembly is exactly the. same asin the first form of the inven- -tion and the same reference numerals have, therefore,

been employedv to designate identical elements or portions of the devices. The endplates are designated at 76 and are provided with upper and lower bores 77 and 78. respectively, through which extend the opposite ends of The inside faces of each. of the-endplates 76 and also the inner periphery of, the bores 77 and-78 may be surfaced with a suitable bearing material 82 as in the first form of the invention. The endv plates 76' are each formed with an innermost counterbore83 and tin-outermost counterbore $4 concentrio with the main bores 77 and 78 and adapted to receive a pair of complementary bearing bushings 86 which extend into the counterbores 83 and 84 as best seen in Fig. 9. Each of the individual bushings 86 is keyed to its end plate 76 by means of a pin 87 to prevent rotation of the bushing relative to the end plate but each bushing is free for limited axial movement relative to the counterbores 83 and 84, as hereinafter described. In this form of the invention the annular pressure chambers, indicated at 88, for pressure loading the end plates 76 are defined by the larger diameter end of the bushings 86 and the adjacent end of the counterbores 84. High pressure working fluid is supplied to the annular chambers 88 and is trapped within each of the chambers 88 by means of a pair of oppositely disposed sealing rings 89 and 90 fitted between the bushings 86 and the counterbore por tions 83 and 84 of the end plates 76. Retaining nuts, indicated at 91, are secured to the opposite ends of the gear shafts for holding the bushings 86 in operative position.

The arrangement for supplying high pressure working fluid to the annular chambers 88 differs slightly from the corresponding arrangement shown in Figs. 1 to 8. Referring to Figs. 11 to 14- particularly, the end plates 76 are each provided with a double set of unidirectional check valves and communicating passageways in order to permit reversible operation of the pump. The inside face of each end plate 76 is formed with a pair of shallow recesses 92 and 93 (Fig. 12) similar to the recesses 61 and 62 in the first embodiment of the invention. For descriptive purposes the recess 92 will be considered as being on the high pressure or discharge side of the pump and the recess 93 as being on the low pressure or inlet side of the pump. A valve chamber or bore 94 (Fig. 14) extends outwardly from the recess 92 through the end plate 76 and contains a pring-pressed ball check valve 96. A similar valve chamber 97 and a check valve 93 are provided adjacent the opposite side edge of the end plate 76 in communication with the recess 93. Extending outwardly from the recesses 92 and 93 are additional valve chambers or bores 99 and 101 disposed intermediate the valve chambers 94 and 97 and provided with oppositely disposed spring-pressed ball check valves 102 and 103, respectively. The valve chambers 99 and 101 terminate short of the outer face of the end plate 76, whereas the valve chambers 94 and 97 have ports providing fluid communication completely through the end plate.

High pressure working fluid passes from the recess 92, opens the valve 102, and flows into the valve chamber 99. Valve 96 is retained in closed position by the pressure of the high pressure fluid. The diameter of the valve chamber or bore 99 is slightly greater than the width of the portion of the end plate structure, indicated at 104, between the upper and lower counterbores 84 whereby to provide a pair of openings or break-throughs 105 extending from the inner end of the valve chamber 99 to each of the counterbores 84 for supplying high pressure fluid to the upper and lower annular pressure chambers 88. A pair of similar break-throughs 106 are formed at the inner end of the valve chamber 101. The valve 98 operates as in the first form of the invention to vent working fluid from the cover chambers of the pump through the recess 93 to the inlet or low pressure side of the pump. Reverse operation of the check valve arrangement will be readily understood without further description.

The lubrication scheme in this embodiment of the invention diflers from the lubricating scheme of the first embodiment primarily in that the leakage of high pres sure fluid is in an outward direction from the gear faceend plate surfaces. Inasmuch as the thrust bushings 36 are keyed to the end plates 76 by means of the pins 87, it will be seen that the retainer nuts 91 at the ends of the gear shafts 79 and'81 rotate relative to the thrust bearings 86, whereas in the first form of the invention the thrust bearings are rotatable in unison with the retaining nuts. Consequently, it is important in this embodiment of the invention to provide adequate lubrication between the inner faces of the nuts 91 and the outer ends of the thrust bearings 86. In addition, adequate lubrication is required for the radial bearing journals of the shafts 79 and 81.

Semi-annular grooves, indicated at 108 (Fig. 12), are provided around the bores 77 and 78 in the end plates 76 at the inside faces thereof. The opposite ends of each of the grooves 108 are placed in fluid communication with the valve chambers 99 and 101 by means of a pair of angular bores 109 extending through the end plate structures, as shown in Fig. 13. Thus, high pressure working fluid which is admitted to the valve chamber 99 from the recess 92 passes through the connecting passageway 109 to the groove 108 and annularly therein to the inlet or low pressure side of the pump whereby to insure adequate lubrication of the gear face-end plate surfaces. Minute radial grooves or scratches, indicated at 111, are also provided between the semi-annular grooves 108 and the bearing journals in order to permit high pressure fluid to flow from the grooves 103 axially along the bearing journals toward the retaining nuts 91.

As seen in Fig. 10, the inside face of each of the nuts 91 is formed with an annular groove 112 and a plurality of intersecting radial grooves 113 whereby lubricating fluid issuing from the radial bearing journals is distributed throughout the entire bearing interface between the nuts 91 and the outer ends of the thrust bearings 86. Thus, high pressure lubricating fluid leaks axially along the radial bearing journals between the thrust bearings 86 and the shafts 79 and 81 and thence flows annularly in the grooves 112 and radially outwardly through the grooves 113 into the low pressure cover chambers 50 and 51. Slight axial movement of the bushings 36 can occur in the event that foreign material occurs in the working fluid or in the event of differential thermal expansion of the parts. In order to further insure lubrication of the thrust bearings, a plurality of holes 114 are provided which extend radially from the inside to the outside of the gear shafts 79 and 81 adjacent the bearing surfaces between the nuts 91 and the thrust bearings 86. During rotation of the shafts 79 and 81, low pressure fluid contained in the axial bores therethrough is thrown outwardly by centrifugal force through the holes 114 and thus passes into the lubricating grooves 112 and 113.

From the foregoing description it will be seen that my invention affords numerous advantages not possessed by the prior art devices of this type. Thus, the unit assembly arrangement of the inner working parts of the pump permits exact clearance adjustment independently of the final assembly of the pump and also facilitates replacement and repair work. In addition, the axial reactions involved in the pressure loading arrangement are transmitted to tension members comprising part of the internal unit assembly and which, in the preferred embodiment of the invention, also comprise the gear shafts. As a. result of this feature, the end cover portions of the pump casingare not subjected to high pressures, and therefore, need not be constructed for the high structural strength purposes required in "the central or body portion of the casing. In addition, the device is readily adapted for reversible operation merely by changing the direction of rotation of the gears.

Although the invention has been described in connection with certain specific embodiments of a gear pump, it will be understood that various alternative and equivalent constructions can be resorted to without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In a gear-type liquid displacement device of the character described, a housing, a pair of end plate structures mounted in said housing in sealing relation therewith and in spaced relation toeach. othen to formwith; said housing a. fluid. chamber thereim, a pair.- of; meshed.

structures to provide a plurality: of confined pressurechambers therebetween, and said. endv plate. structures having fluid passagewaysextending from said. fluid charm-- ber tosaid pressure chambers whereby to urgesaid end plate structures inwardly against the gears. by meansof fluid under pressure.

2. In a gear-type liquid. displacement device of the character described, a pair of meshed gears, movable end plate means disposed at the opposite faces of said. gears, a pair of gear shafts carrying. said gears and extending at their opposite ends'through said. end plate means in journaledrelation therewith,, axially movable thrust bearing means on said shafts adjacent the ends. thereof for coacting with said end plate means, and retaining means adjustablysecured tov the ends of said shafts for retaining said thrust bearing. means in predetermined.

operative relation with said end. plate means. whereby. the forces urging said end plate means outwardly from said gears during operation. of the device are trans-i mitted axially to said gear shafts thereby placing the latter under tension.

3. In a gear-type liquid displacement device of the character described, meshed gears, 21 pair of movable end plate meaus disposed at. the opposite faces of said. gears, a pair of gear shafts carryingsaid gears and extend.- ing at their opposite ends through. said end'platemeans in. journaled relation therewith, thrust bearing means on said shafts adjacent the ends thereof for coacting with. said end plate means, said thrust bearing means having portions spaced from and cooperable with the adjacent end plate means to provide annular pressure chambers therebetween adapted to receive fluid under pressure for urging the end plate means inwardly toward saidlgears, and retaining rneans secured to said shafts for retaining said thrust bearing means in operative relation with said end plate means whereby the forces urging said end plate means and said thrust bearing means outwardly from said gears during operation of the device are transmitted axially to said gear shafts thereby placing the latter under tension.-

4. In a gear-type liquid displacement" device of the character described, a casinghaving a fluid inlet and outlet, a pair of meshed gears in said casing, a pair of movable end plates disposed at the opposite faces of said gears within said casing in sealing'rel'ation with the latterwhereby to define with said casing a high pressure fluid chamber and a low pressure fluid chamber at opposite sides of a plane passing throughthe axes of saidgears, a pair of gear shafts carrying said gears and extending at their opposite ends through. said end plates in journaled relation therewith, annular thrust bearing means' on: said shafts adjacent the ends thereof; said thrust" bearing means having portions spaced from the adjacent end plate structures whereby to providea plurality of annular pressure chambers therebetween, retaining means on said shafts for retaining said thrust bearing means in operative? outlet, a pair of meshed gears in said. casing-,.-a pair of; movable end plates disposed atJtheo posite faces-rof saidigears; within-said. casing in sealing. relation withthe latter whereby to define with said. casing; a high pressure. fluid:

chambers-and. a low pressure fluid chamber at. opposite sides of a-planepassingthrouglr the axes of said gears, a pair of gear shafts carrying said. gears and extending. at their opposide. ends through said. endplates in journaled relation therewith, thrust bearing means on said shafts adjacent the ends thereof and having portions spaced fromthe adjacent end plate structures whereby toprovidea plurality of annular pressure chambers therebetween, retaining means on said shafts for retaining said thrust bearing; means in operative relation with said end plates, aud-means-in said end plates providingfluid communication between. said high pressure fluid chamberv and said annular pressure. chambers whereby to urge said end plates inwardly against said gears in operative relation therewith,.the relationship of the areas at the inner and outer faces of said endxplates which are acted upon by fluid pressure in. said-high pressurefluid chamber and in said. annular pressure chambers, respectively, being such that the forces acting on the outer faces ofv said end plates and urging the latter against the gears: are: slightly greater than the forces: acting onthe inner faces of said. end plates.

6; A gear. pumpcomprising a housing'having a central pumping; chamber with an inlet at one; side thereof and an? outlet at the. other side, a pair of meshed gears in said;- pumpingchamber, a pair'of movable end platesfittingclosely within said. pumping chamber'at the opposite faces. of; said gears, said housing also comprising a pair. of. endcover portions at opposite ends of. said pumping chamber in: spaced relation from saidend plates, a pair of gear shafts carrying, said gears and extending. at their opposite ends through said end platesin jonrnaled rela tion therewith, thrust bearing means secured on said shafts at the ends thereofand having portions cooperable with the adjacent. end plate structures. to provide a plurality of. confined annular pressure chambers therebetween, and means in said end plates. providing fluid communication betweenv said pumping chamber and said meshed gears in'said'body portion between said inlet and" outlet, a pair of movable end plates fitting closely in sealing relation within said body'portion at the opposite faces of said gears and providing a' pumping chamber in said. central body portion between said end plates, said end plates: being spaced inwardly from said cover portionsto define a pair of cover chambers'therebetween and said gearszhaving. gear shaftsextending at their opposite endstthroughsaidend plates into said cover chambers, thrust bearing means secured on said shafts at the opposite ends thereof; and having portions cooperable with the adjacent: end plates-toprovide' a plurality of confined annular pressure chambers. therebetween, and means in each of. saidend plates for'supplyingflhid under pressure from. said pumping chamber to said annular pressure chambers whereby said' end plates are pressure loaded and urged inwardly against said gears and the reaction from said pressureloadingiis taken up bysaid gear'shaft's without: imposing the same onsaid cover portions of said housing 8. A gear pump. comprising a housing having a central body portion withv a fluidinlet andoutlet and end cover portions at opposite endsof said body portion, a pair of meshing; gears. in said. body portion between said inlet and. outlet',.a pair of movable endplates fitting closely in sealing relation within said body portion at the opposite facestof said. gears and providing a pumping chamber in said: centrala body. portion between said endplates, said am nes end plates being spaced inwardly from said cover portions to define a pair of cover chambers therebetween and said gears having gear shafts extending at their opposite ends through said end plates into said cover chambers, thrust bearing means secured on said shafts at the opposite ends thereof and having portions cooperable with the adjacent end plates to provide a plurality of confined annular pressure chambers therebetween, said thrust bearing means also having portions rotatable with said shafts, means for supplying fluid to the rotating portions of said thrust bearing means for lubricating the same, said thrust bearing means being adapted to permit leakage of said fluid past said rotating portions into said cover chambers, means in each of said end plates for supplying fluid under pressure from the outlet side of said pumping chamber to said annular pressure chambers for urging said end plates inwardly, and pressure control means in each of said end plates for venting fluid from said cover chambers to the inlet side of said pumping chamber.

9. A gear pump comprising a housing having a central body portion with a fluid inlet and outlet and end cover portions at opposite ends of said body portion, a pair of meshed gears in said body portion between said inlet and outlet, a pair of movable end plates fitting closely in sealing relation within said body portion at the opposite faces of said gears and providing a pumping chamber in said central body portion between said end plates, said end plates being spaced inwardly from said cover portions to define a pair of cover chambers therebetween and said gears having gear shafts extending at their opposite ends through said end plates into said cover chambers, thrust bearing means secured on said shafts at the opposite ends thereof and having portions spaced from and cooperable with the adjacent end plates to provide a plurality of confined annular pressure chambers therebetween, means for supplying fluid to said thrust bearing means for lubrication thereof and including means for permitting leakage of said fluid into said cover chambers, unidirectional .valve means in each of said end plates communicating between the outlet side of said pumping chamber and said annular pressure chambers for supplying fluid under controlled pressure to the latter whereby said end plates are pressure loaded and urged inwardly against said gears and the reaction from said pressure loading is imposed on said gear shafts and not on said cover portions of said housing, and additional unidirectional valve means in each of said end plates for venting fluid from said cover chambers to the inlet side of said pumping chamber.

10. A gear pump comprising a housing having a cenchamber in said central body portion between said end plates, said end plates being formed with a pair of spaced bores and said gears having gear shaftsextending at their opposite ends through said bores in journaled relation therein, said end plates also being spaced inwardly from said cover portions to define a pair of cover chambers therebctween, a plurality of annular thrust collars mounted on said gear shafts, said collars having portions bearing against the adjacent'end plates and having portions spaced from said end plates to provide a plurality of confined annular pressure chambers therebetween adapted to receive fluid under pressure, a plurality of retaining nuts threaded at the ends of said gear shafts and engaging said thrust collars for retaining the latter in rotating bearing relation with the end plates, said retaining nuts being adjustable on said gear shafts for determining the maximum clearance between said end platesand the gear faces, means in each ofsaid end platesfor supplying fluid under pressure from the outlet side of said pumping chamber to said annular pressure chambers whereby to urge said end plates inwardly against the gear faces, said fluid being adapted to flow from said annular pressure chambers along the gear shaft journals through the end plate-gear bearing surfaces and into the outlet side of said pumping chamber for lubricating the journals, said thrust collars permitting leakage of said fluid between the thrust collar-end plate bearing surfaces into said cover chambers, and means in each of said end plates for venting fluid from said cover chambers to the inlet side of said' pumping chamber.

11. A gear pump comprising a housing having a central. body portion with a fluid inlet and outlet and end cover portions at opposite ends of said body portion, a pair of meshed gears in said body portion between said inlet and outlet, a pair of movable end plates fitting closely in sealing relation within said body portion at the opposite faces of said gears and providing a pumping chamber in said central body portion between said end plates, said end plates being spaced inwardly from said cover portions to define a pair of cover chambers there between and said end plates also being provided with a pair of spaced bores and a pair of counterbores extending inwardly from the outer face of said end plates, a plurality of. annular thrust bushings fitted into said counterbores, said thrust bushings having portions spaced from the adjacent end plate structures to define a plurality of annular pressure chambers therebetween and said thrust bearings being keyed to said end plates to prevent rotation thereof but permitting limited axial movement thereof, a pair of gear shafts carrying said gears and extending at their opposite ends through said bores and said thrust bushings in journaled relation therein, a plurality of retaining nuts secured to the ends of said gear shafts in rotating bearing relation with said thrust bushings for retaining the latter in place, means in each of said end plates for supplying fluid under pressure from the outlet side of said pumping chamber to said annular pressure chambers whereby to urge said .end plates inwardly against the gear faces, said fluid being adapted to flow from the outlet side of said pumping chamber through the end plate-gear face bearing surfaces along the gear shaft journals and thence through the retaining nut-thrust bushing bearing surfaces into said cover chambers whereby to provide lubrication for the shaft journals and the thrust bushings, and means in each of said end plates for venting fluid from said cover chambers to the inlet side of said pumping chamber.

12. The device of claim 11 further characterized in that said gear shafts are formed with axial bores providing fluid communication between the oppositely disposed cover chambers, said retaining nuts are formed with interconnected annular and radial grooves at their inner faces to facilitate lubrication thereof, and said shafts are provided with a plurality of apertures extending radially from said axial bores to said grooves to supply further lubrication for said nuts.

13. In a gear-type liquid displacement device of the character described, a housing having a fluid inlet and outlet with a gear chamber therebetween, a pair of meshed gears mounted in said gear chamber, coacting end plate means mounted in sealing relation within said housing at opposite faces of said gears and rotatably supporting said gears, thrust means disposed against at least one of said end plate means and having a portion thereof spaced from and cooperable with said one end plate means to provide a fluid pressure loading chamber therebetween, means for supplying fluid under pressure to said loading chamber for urging said one end plate means inwardly toward said gears, and tension members extending between said end plate means and operatively secured to said thrust means and coacting with the other of said end plate means whereby the fluid pressure in said loading chamber also urges said other end plate means inwardly toward said gears and whereby the reacgreases 1 3; tionforces from the pressure loading, of said: end plate means" are imposed on said tension members without applying the same to said housing.

14. In a gear-type liquid displacement device of the character described, a housing, a pair of end plate structures movably mounted in said housing in seali'ng relation therewith and in spaced relation to each other to form with said housing a fluid chamber therein, a-pair of meshed gears mounted in said chamber between said end plate structures, a pair of gear shafts carrying said gears and having their opposite ends extending through and journaled in said end plate structures, an axially movable thrust means adjustably supported on said shafts at the ends thereof in operative relation with said end plate structures whereby to retain the latter in predetermined operative relation with said gears-and whereby the forces tending to urge. said end plate structures outwardly from said gears during operation of the device are transmitted-axially to saidgear'shafts thereby placing the latter under tension.

In a gear-type liquid displacement device of. the character described, an internal unit assembly comprising; a pair of meshed gears, coacting end plate means mounted at opposite faces of said gears and rotatably supporting said gears, thrust means disposedv against; at least one of said end plate means and having aportionthereof spaced from and cooperable with said one end platemeans to provide a fluid pressure loading chamber therebetween, means for supplying fluid under pressure, to said loading chamber for urging said one end plate means inwardlytoward said gears, and tension members extending between said end plate means and operatively secured to said thrust means and. operatively coacting with, the other of. said end plate means whereby. the fluid pressure in said loading chamber also urges.- said other end? plate means inwardly toward said gears and whereby the reaction forces from the pressure loading of said end plate means are imposed on and resisted by said tension members.

16. In a gear-type liquid displacement device of the character described, an internal unit assembly comprising a pair of meshed gears, a pair of coacting end plate means mounted at opposite faces of said gears and rotatably supporting said gears, thrust means disposed against each of said end plate means and having portions spaced from and cooperable with the end plate means for providing a pair of confined fluid pressure loading chambers therebetween, means for supplying fluid under pressure to said loading chambers for urging said end plate means inwardly toward said gears, and tension members extending between said end plate means and operatively secured to said thrust means whereby the reaction forces from the pressure loading are imposed axially on and resisted by said tension members.

17. In a gear-type liquid displacement device of the character described, a pair of meshed gears, a pair of end plate structures disposed at the opposite faces of said gears, a pair of gear shafts carrying said gears and having their opposite ends journaled in the respective end plate structures, and thrust means mounted on said shafts at the ends thereof in cooperating relation with said end plate structures whereby to retain the latter in operative relation with said gears, said thrust means having portions spaced from the adjacent end plate structures to provide a plurality of confined pressure chambers therebetween adapted to be supplied with fluid under pressure for urging said end plate structures inwardly toward the gears, and the forces tending to urge said end plate structures and said thrust means outwardly from said gears during operation of the device being transmitted axially to said gear shafts thereby placing the latter under tension.

18. A gear-type liquid displacement device comprising a housing, a pair of meshed gears in said housing, a pair of movable end plates mounted at the opposite faces of said gears and providing within" saidv housing a pump.- v

ing chamber, means in said housing: providing a fluid inlet and outlet for said pumping chamber, a pair of gear shafts carrying said. gears and extending at their opposite ends in journaled relation through said. end plates, said end plates being spaced inwardly from the ends: of said housing to define a pair of end chambers therebetween, thrust means mounted on said shafts at the endsth'ereof and having portions spaced from said end plates to provide a plurality of confined pressure chant-- bers therebetween adapted to receive fluid under pressure, means in each of said end plates for supplying fluid under pressure from the outlet side of said pumping charm her. to said pressure chambers whereby to urge said end" plates inwardly against the gear faces, said fluid being adapted to flow from said annular pressure chambers along the. gear shaft journals through the e'nd'plate-gearface bearing surfaces and into the outlet side of saidpumping chamber for lubricating the journals, said thrust means permitting leakage of said fluid: from said pressure chambers intosaid en'd chambers, and means in. each of said end plates for venting fluid from said end chambers to. the inlet side of said. pumping chamber.

19. A'gear-type liquid displacement device comprising a housing with:a fluid inlet and outlet, a pair of meshed gears in said housing between said inlet and outlet, a pair of movable end plates mounted at the opposite faces of said, gears and: providing within said housing a pumping. chamber, said end plates being spaced'inwardly from the ends of said housing to define a pair of end 61121111- bers therebetween and said end plates being provided with a pair of spaced bores and a pair of counterbores extending inwardly from the outer faces of said end plates, thrust means fitted into said counterbores and hav-- ing portions; spaced from the adjacent end-plate structures to define a plurality of confined pressure chambers therebetween, said thrust means being keyed to said end plates to prevent rotation thereof, a pair of gear shafts carrying said gears and extending at their opposite ends through said bores and said thrust means in journaled relation therein, means secured to the ends of said gear shafts for axially retaining said thrust means, means in each of said end plates for supplying fluid under pressure from the outlet side of said pumping chamber to said pressure chambers whereby to urge said end plates inwardly against the gear faces, said fluid being adapted to flow from the outlet side of said pumping chamber through the end plate-gear face bearing surfaces along the gear shaft journals and thence into said end chambers whereby to provide lubrication for the shaft journals, and means in each of said end plates for venting fluid from said end chambers to the inlet side of said pumping chamber.

20. A gear-type liquid displacement device comprising a housing with a fluid inlet and outlet, 21 pair of meshed gears in said housing between said inlet and outlet, 21 pair of movable end plates mounted at the opposite faces of said gears and providing within said housing a pumping chamber, said end plates being provided with a pair of spaced bores and a pair of counterbores extending inwardly from the outer faces of said end plates, thrust means fitted into said counterbores and having portions spaced from the adjacent end plate structures to define a plurality of confined pressure chambers therebetween adapted to be supplied with fluid under pressure for urging the end plates inwardly toward the gear faces, said thrust means being keyed to said end plates to prevent rotation thereof but permitting limited axial movement thereof, a pair of gear shafts carrying said gears and extending at their opposite ends through said bores and said thrust means in journaled relation therein, and means secured to the ends of said gear shafts for axially retaining said thrust means.

21. In a gear-type liquid displacement device of the character described, a housing comprising a central body portion and a pair of end cover portions; an internal unit assembly comprising the working parts of the device and removable as a unit from said housing; said unit assembly including a pair of meshed gears, a pair of end plates disposed at the opposite side faces of said gears, bearing means carried by said end plates for rotatably supporting said gears, thrust means disposed against at least one of said end plates and having a portion spaced from said one end plate to provide a confined pressure loading chamber therebetween, means for supplying fluid under pressure to said loading chamber for applying a predetermined inward pressure against said one end plate, and a tension member extending between said end plates and operatively secured to said thrust means and coacting with the other of said end plates whereby the fluid pressure in said loading chamber also urges said other end plate inwardly and whereby the reaction forces from the pressure loading of the end plates are imposed on said tension member without applying the same to said end cover portions of the housing; and sealing means disposed between said central body portion of said housing and the opposite ends of said unit assembly for sealing the same in the central body portion of said housing.

22. In a gear-type liquid displacement device of the character described, a housing comprising a central body portion and a pair of end cover portions; an internal unit assembly comprising the working parts of the device and removable as a unit from said housing; said unit assembly including a pair of meshed gears, a pair of end plates disposed at the opposite side faces of said gears and spaced inwardly from said cover portions whereby to define a pair of cover chambers at the opposite ends of said central body portion, bearing means carried by said end plates for rotatably supporting said gears, thrust and having a portion spaced from said one end plate to provide a confined pressure loading chamber therebetween, means for supplying fluid under pressure to said loading chamber for applying predetermined inward pressure against said one end plate, and a tension member extending between said end plates and operatively secured to said thrust means and coacting with the other of said end plates whereby the fluid pressure in said loading chamber also urges said other end plate inwardly and whereby the reaction forces from the pressure loading of the end plates are imposed on said tension member without applying the same to said cover chambers and the end cover portions of said housing; and a pair of sealing rings extending around said unit assembly at the junctures of said end plates with the central body portion and the cover portions of said housing whereby to seal said centralbody portion from said cover chambers.

References Cited in the, file of this patent UNITED STATES PATENTS 2,082,412 Morton June 1, 1937 2,176,322 Barrett Oct. 17, 1939 2,236,980 Ungar Apr. 1, 1941 2,321,609 Marco June 15, 1943 2,367,463 Heimbach Ian. 16, 1945 2,372,816 Deschamps et a1. Apr. 3, 1945 2,412,588 Lauck Dec. 17, 1946 2,420,622 Roth et a1. "-3. May 13, 1947 2,444,165 Lauck June 29, 1948 2,470,355 Lauck May 17, 1949 2,527,941 Lauck et a]. Oct. 31, 1950 FOREIGN PATENTS 62,290 Denmark May 30, 1944 455,698 Great Britain 1936 541,601 Great Britain Dec. 3, 1941 

